Subject: [FlyRotary] Re: evap core versus radiator


> Posted for "sqpilot@earthlink" <sqpilot@earthlink.net>:
>
>
> > So a 9x10.5x3.6 GM core turns out to be pretty close to what the
equations
> > indicate in required for that power and airspeed.  Actually perhaps a
bit
> > thicker at 3.64 inch than optimum at 120 MPH according to the equations.
> So
> > the 3" thick core could be a bit closer to optimum if using a GM type
core
> > than the 3.6" core for 120MPH cooling and would probably improve cooling
> in
> > the take-off and initial climb phase where there is less dynamic
pressure
> to
> > force air through the cores.
>
>
>
>   Hi, Ed....Do I understand correctly that only one of these cores would
be
> needed to cool 160 HP at 120 MPH?  Thanks.  Paul Conner
>

Hi Paul,

    No - sorry if I misled you.  Unless the pass several weeks of studying
K&W are for naught, its fairly clear that for 160HP at 120MPH you need two
GM cores.  The point I was trying to make is that the calculations show that
for the frontal area of the GM cores that their optimum thickness for 120
MPH is closer to 3" or the core you mentioned to Marv rather than the GM
cores 3.6".

I have however progress to the point (I think) where I could calculate the
effectiveness of other cores (like car type radiators) in providing cooling.
The only problem would be I would need some parameters that are normal not
available.  One is the ratio of open area to frontal area of the core.
Similarly the dimensions of the holes (air passages) (width and height) as
well as the normal dimensions (width Height thickness).  Also whether the
fins are smooth, slotted (the cores fins are slotted) or corrugated.

I obtained those dimension from the GM core and the calculated results
appears to be close to what folks are observing.

Found an old Naca paper translated from a German study written back in 1939
that is surprisingly similar to the K&W work.   It does have some different
stuff, a bit more on the use of cowl flaps which is interesting.  Also, it
shows that as the radiator heats up, it offers more air resistance and less
cooling effectiveness and that the area of the cowl flap opening is
important in getting good results from them.

Ed Anderson